1. Field of the Invention
The present invention relates to integrated circuits. More, particularly, this invention relates to reducing spacing between a bus and adjacent circuits. Still more particularly, this invention relates to defining slots in the bus during design of an integrated circuit to reduce the space needed between the bus and adjacent circuitry.
2. The Prior Art
As the electrical arts advance, the amount of circuitry in an integrated circuit is increasing. Therefore, it is a problem for those that design integrated circuits to maximize the space in an integrated circuit where circuitry can be placed.
Currently, designers of integrated circuits are limited by the spacing requirements between a bus and circuits that are adjacent to the bus in the integrated circuit. For purposes of this discussion, a bus is a strip or line of conductive material which carries signals between circuits and a circuit is any configuration of circuitry that is in the integrated circuit. Also, for purposes of this discussion, conductive material is a metal or other type of substance having properties that allow transmission of electric signals.
The present design process requires a designer to place a solid strip of conductive material in a layer of the integrated circuit. The designer must than use the properties of the solid strip of conductive material to determine the spacing between the strip and a circuit that is adjacent to the strip. The designer then places the circuit adjacent to the bus with the determined amount of spacing separating the circuit from the bus.
FIG. 1 illustrates the above-described configuration. In layer 100 of an integrated circuit, a bus 101 is a solid strip of conductive material. Circuit 102 and circuit 103 are adjacent to bus 101 on opposite sides of bus 101. Circuit 102 and circuit 103 are both separated by distance D, represented by arrows 104 and 105, from bus 101. Distance D is determined from the width of bus 101. The width of bus 101 is used to determine the density of the conductive material in bus 101 which dictates the distance D of separation that must be maintained by the bus and an adjacent circuit.
After the circuit is designed with the bus made of a solid strip of conductive material. The design is provided to the manufacturer. The manufacturer then cuts slots into the strip of conductive material of the bus. The slots remove conductive material to change the density of conductive material in the bus and make the bus more manufacturable.
FIG. 2 illustrates a layer 200 of integrated circuit after the routing is completed in the manufacturing process. In layer 200, bus 100 is a strip of conductive material that has slots 201 in the strip. Each slot 201 is devoid of conductive material. The slots change the amount of conductive material in the strip, which in turn changes the density of the material. However, the distance, D, between the bus and adjacent circuits 102,103 has not been changed. Therefore, circuits 102 and 103 are further away from the bus than is needed.